A series of InAs epitaxial layers with thicknesses ranging from 0.5 up to 6.2 μm was grown on (100) oriented semi-insulating GaAs substrates by molecular beam epitaxy. The transport properties of the layers have been investigated by Hall effect measurements down to 10 K. The properties of the films are greatly influenced not only by the growth conditions but also by the InAs/GaAs interface structure. The mobility at room temperature is 1.8×104 cm2/V s (n=6.1×101 5 cm-3) and peaks at about liquid-nitrogen temperature with a value of 5.173×104 cm2/V s (n=3.1×1015 cm-3) for a 6.2-μm-thick InAs layer. It is shown that the temperature dependence as well as the magnitude of the mobility can be explained by a combined impurity-phonon-dislocation scattering mechanism. From the combination, dislocation densities of the order of 106 cm-2 are found.